1. Field of the Invention
The present invention relates to a wireless communication system, and more particularly, to a method of operating a sleep mode in a wireless communication system.
2. Discussion of the Related Art
Generally, a power of a user equipment is dependent on a battery for mobility. And, it is very important to reduce power consumption of the user equipment. Various methods have been proposed to reduce the power consumption. And, one of the various methods related to a sleep mode.
In the sleep mode, power consumption can be reduced in a manner of holding an operation of a user equipment having no more traffic to transceive with a base station.
In case of having no more traffic to transceive with a base station in the course of performing communication with the base station in normal or active mode, a user equipment sends a sleep request (hereinafter named MOB_SLP-REQ) for entering a sleep mode to the base station. Having received the MOB_SLP-REQ message, the base station sends a sleep response (hereinafter named MOB_SLP-RSP) including such parameters related to the sleep mode of the user equipment as an initial sleep cycle, a listening window and the like to the user equipment.
Having received the MOB_SLP-RSP message, the user equipment enters the sleep mode using the parameters related to the sleep mode.
During the sleep mode, the user equipment alternately repeats a sleep interval and a listening interval. The user equipment is able to transceive data with the base station for the listening interval but is unable to transceive data with the base station. Therefore, data arriving at the base station is buffered during the sleep interval.
According to a related art, the user equipment stays in a listening state during the listening window included in the MOB_SLP-REQ message. Therefore, even if the base station has no data to transmit to the user equipment, the user equipment keeps maintaining the listening state during the listening window included in the MOB_SLP-REQ message, thereby wasting its power.
As mentioned in the foregoing description, according to the related art, even if a base station has no data to transmit to a user equipment, the user equipment keeps maintaining a listening state, thereby wasting its power.